Catheters are commonly used in medicine for delivery of fluids, therapeutics and implants as well as in sampling tissues and bodily fluids. Catheters can be constructed with balloons or other tools to dilate tissue, block fluid flow or isolate segments of the anatomy. A relatively common use for a catheter is the delivery of drugs to a target tissue using blood vessels as a means of access. When a balloon is used, the vascular compartment distal to the balloon is isolated from the vascular compartment proximal to the balloon and perfusion of diagnostic, therapeutic or embolic agents is localized and concentrated. Transvascular catheters, especially in the peripheral blood circulation, need to have a small axial diameter to allow access into small vessels.
One common use for a microcatheter is the delivery of embolic agents and anticancer drugs to a tumor.
According to the NIH, 30,640 people were diagnosed with primary liver cancer (hepatocellular carcinoma, HCC) and 142,820 people were diagnosed with colorectal cancer in the US in 2013. Seventy five percent of these will metastasize to the liver. Liver resection and transplant are the only curative means; however, only small numbers of patients are eligible. Systemic Chemotherapy for primary and metastatic tumors in the liver is ineffective, having a response rate of about 20% and a survival benefit of 10.7 months vs. 7.9 months over symptomatic care.
Trans-Arterial Embolization therapy is the transvascular injection of drug and/or embolic agents directly into, or in the vicinity of, the tumor vasculature using a microcatheter. Embolization therapy causes a shutdown of blood flow and, when drug or radioactivity is present, simultaneous release of high concentrations of drug or radioactivity. The technique is also noted for its very low level of toxicity. Chemoembolization was established as a standard of care for intermediate stage hepatocellular carcinoma in 2006.
Numerous studies have demonstrated transarterial embolization to be effective on a number of primary cancers and to have better performance than chemotherapy for both HCC and metastatic colorectal cancers in the liver; however, studies show inconsistent outcomes with reported tumor responses from 15% to 85%. Although anatomical and individual differences are clearly of significance in between-patient variation, clinical studies, each of which include a range of patients, show very different outcomes, indicating that procedural standardization is needed.
The present state-of-the-art embolization therapy for tumors in the liver relies on high volume “forward flow” from the hepatic artery that is flowing at about 6 ml/sec to deliver embolization agents into the tumor. As embolization progresses, the distal capillaries become occluded and the tumor can no longer accept this high flow rate, even though the tumor is only partially filled with embolic agents. Tumor embolization using high volume flow from the unrestricted hepatic artery causes: (1) rapid embolization of the distal portions of tumor capillaries, (2) rapid onset of high intra-tumor pressure, (3) reflux of blood and embolic agents from the tumor, (4) increased non-target flow into hepatoenteric arteries, and (5) poor filling and distribution of embolic agents in the tumor. This situation results in an uncontrollable number of particles or other embolic agents entering the tumor and high procedural variability.
Although standardization to an optimal protocol should improve reproducibility and overall outcomes, the procedure is presently without optimization or standardization. The current delivery catheters are unable to control many of the above mentioned variables, making standardization unlikely. There is a need for a delivery system that enables a measurable clinical endpoint, a known quantity of embolic agent delivered, and elimination of non-target embolization. This is a required first step if standardization is to be achieved.
As a requirement, a delivery catheter that would solve the aforementioned problems, must have a small radial diameter to allow access into small vessels that are typically in the vicinity of the tumor. Presently, balloons are bonded to the external surface of a catheter and necessarily increase its diameter. It would be a significant advantage to construct a balloon catheter whereby a balloon was positioned below the surface of the catheter when in its constrained configuration and return thereto following inflation and deflation. One method to accomplish this is to configure a circumferentially oriented pocket or pockets in a catheter whereby a balloon bonding surface is positioned below the surface of the catheter. The present disclosure is a device and method that achieves a low profile catheter by positioning the balloon bonding surfaces below the surface of a drug delivery catheter.
U.S. patent application Ser. No. 10/128,977 describes a coaxial catheter whereby a balloon is bonded to an elongated outer tube to prevent the balloon from telescopingly buckling when the balloon is being pushed across a narrow passage. U.S. Pat. No. 6,066,157 describes a coaxial coronary angioplasty catheter whereby an anchor joint is configured to allow distal movement of the inner tube and to prevent proximal movement. U.S. Pat. No. 5,647,198 describes a catheter with a pair of spaced apart balloons that define an intra-balloon space. A lumen passes through the catheter and exits within the intra-balloon space allowing injection of drugs, emulsions, fluids and fluid/solid mixtures. A perfusion lumen or bypass extends from a location proximal to the proximal balloon and to the distal tip to allow shunting of blood past the inflated balloons. U.S. Pat. No. 5,674,198 describes a two balloon catheter that is designed for treating a solid tumor. The balloons are positioned to isolate the blood flow into the tumor and allow injection of a vaso-occlusive collagen material to block the tumor blood supply. Clifton et al. (1963) Cancer 16:444-452 describes a two balloon catheter for the treatment of lung carcinoma. The four lumen catheter includes a lumen for independent injection in the space between the balloons. Rousselot et al. (1965) JAMA 191:707-710 describes a balloon catheter device for delivering anticancer drugs into the liver. See also U.S. Pat. No. 6,780,181; U.S. Pat. No. 6,835,189; U.S. Pat. No. 7,144,407; U.S. Pat. No. 7,412,285; U.S. Pat. No. 7,481,800; U.S. Pat. No. 7,645,259; U.S. Pat. No. 7,742,811; U.S. App. No. 2001/008451; U.S. App. No. 2001/0041862; U.S. App. No. 2003/008726; U.S. App. No. 2003/0114878; U.S. App. No. 2005/0267407; U.S. App. No. 2007/0137651; U.S. App. No. 2008/0208118; U.S. App. No. 2009/0182227 and U.S. App. No. 2010/0114021.
What is needed and is not provided in the prior art is a means of positioning of balloon bonding surfaces and attachment of a balloon below the surface of a catheter body and allow a low profile catheter that is useful in providing therapy within small blood vessels.